Formulation of an organic functional material

ABSTRACT

The present invention relates to formulations containing at least one organic functional material and at least a first organic solvent, wherein said first organic solvent is an alkyl benzoate solvent, as well as to electronic devices prepared by using these formulations.

TECHNICAL FIELD

The present invention relates to formulations containing at least oneorganic functional material and at least a first organic solvent,wherein said first organic solvent is an alkyl benzoate, as well as toelectroluminescent devices prepared by using these formulations.

BACKGROUND ART

Organic Light Emitting Devices (OLEDs) have been fabricated for a longtime by vacuum deposition processes. Other techniques such as inkjetprinting have been recently thoroughly investigated because of theiradvantages such as cost savings and scale-up possibilities. One of themain challenges in multi-layer printing is to identify the relevantparameters to obtain a homogeneous deposition of inks on the substrate.To trigger these parameters, such as surface tension, viscosity orboiling point, some additives can be added to the formulation.

Technical Problem and Object of the Invention

Many solvents have been proposed in organic electronic devices forinkjet printing. However, the number of important parameters playing arole during deposition and the drying process makes the choice of thesolvent very challenging. Thus, the formulations containing organicsemiconductors used for deposition by inkjet printing still need to beimproved. One object of the present invention is to provide aformulation of an organic semiconductor which allows a controlleddeposition to form organic semiconductor layers having good layerproperties and efficient performance. A further object of the presentinvention is to provide a formulation of an organic semiconductor whichallows a uniform application of ink droplets on a substrate when usede.g. in an inkjet printing method thereby giving good layer propertiesand efficient performance.

In WO 2005/083814 A1, solutions of at least one organic semiconductorcontaining at least one high-molecular weight constituent in a solventmixture of at least three different solvents A, B and C are disclosed.Solvents A and B are good solvents for the organic semiconductor,solvent C is a bad solvent for the organic semiconductor. As solvent B,propyl benzoate and butyl benzoate are disclosed.

In WO 2006/087945 A1, a film-forming composition is disclosed, which isa composition to form a film of a hole-injecting/transporting layer ofan organic electroluminescent device, wherein the film-formingcomposition contains a hole-injection and/or transport material and/oran electron-accepting compound and a liquid in which the material and/orthe compound have been dissolved; the liquid is based on a solvent whichcontains an aromatic ring and/or an aliphatic ring and an oxygen atomand which has either a boiling point of at least 200° C. or a vaporpressure of 1 torr at 25° C. or lower (referred to as “first solvent”),and the amount of the first solvent contained in the composition is 3 wt% or more. As one first solvent, ethyl benzoate is disclosed.

In WO 2010/010337 A1, a composition adapted for use in the manufactureof an organic light-emissive device is disclosed. The composition isdeposited by passing it through one or more openings under pressure, thecomposition comprising a semiconductive organic host material; aluminescent metal complex, and solvent components, said solventcomponents consisting of methyl benzoate, butyl benzoate, and methylanisole.

Solution to Problem

The above objects of the present invention are solved by providing aformulation comprising at least one organic functional material and atleast a first organic solvent, wherein said first organic solvent is analkyl benzoate.

Advantageous Effects of Invention

The inventors have surprisingly found that the use of an alkyl benzoateas a first solvent allows an effective ink deposition to form uniformand well-defined organic layers of functional materials which have goodlayer properties and performance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a typical layer structure of a device containing asubstrate, an ITO anode, a hole-injection layer (HIL), a hole-transportlayer (HTL), a green-emissive layer (G-EML), a hole blocking layer(HBL), an electron-transport layer (ETL) and an Al cathode.

DESCRIPTION OF EMBODIMENTS

The present invention relates to a formulation containing at least oneorganic functional material and at least a first organic solvent,wherein said first organic solvent is an alkyl benzoate and the contentof the alkyl benzoate is in the range from 50 to 100 vol.-%, based onthe total amount of solvents in the formulation.

PREFERRED EMBODIMENTS

In a preferred embodiment, the first organic solvent is an alkylbenzoate according to general formula (I)

wherein

-   R¹ is identical or different at each occurrence, and are D, F, Cl,    Br, I, NO₂, ON, a straight-chain alkyl having from 1 to 20 carbon    atoms or a branched or cyclic alkyl group having from 3 to 20 carbon    atoms, in which one or more non-adjacent CH₂ groups may be replaced    by —O—, —S—, —NR³—, —CONR³—, —CO—O—, —C═O—, —CH═CH— or —C≡C—, and in    which one or more hydrogen atoms may be replaced by F, or an aryl or    heteroaryl group which has from 4 to 14 carbon atoms and may be    substituted by one or more nonaromatic R³ radicals, and a plurality    of substituents R³, either on the same ring or on the two different    rings, may together in turn form a mono- or polycyclic, aliphatic,    aromatic or heteroaromatic ring system, which may be substituted by    a plurality of substituents R³;-   R² is a straight-chain alkyl group having from 1 to 20 carbon atoms    or a branched or cyclic alkyl group having from 3 to 20 carbon    atoms, in which one or more non-adjacent CH₂ groups non-adjacent to    the —CO—O— group in general formula (I) may be replaced by —O—, —S—,    —NR³—, —CONR³—, —CO—O—, —C═O—, —CH═CH— or —C≡C—, and in which one or    more hydrogen atoms may be replaced by F, or an aryl or heteroaryl    group which has from 4 to 14 carbon atoms and may be substituted by    one or more nonaromatic R³ radicals, and a plurality of substituents    R³, either on the same ring or on the two different rings, may    together in turn form a mono- or polycyclic, aliphatic, aromatic or    heteroaromatic ring system, which may be substituted by a plurality    of substituents R³;-   R³ are identical or different at each instance, and are a    straight-chain alkyl or alkoxy group having from 1 to 20 carbon    atoms or a branched or cyclic alkyl or alkoxy group having from 3 to    20 carbon atoms, in which one or more non-adjacent CH₂ groups may be    replaced by —O—, —S—, —CO—O—, —C═O—, —CH═CH— or —C≡C—, and in which    one or more hydrogen atoms may be replaced by F, or an aryl or    heteroaryl group which has from 4 to 14 carbon atoms and may be    substituted by one or more nonaromatic R³ radicals and-   n is 0 to 3, preferably 0 or 1 and more preferably 0.

In a more preferred embodiment, the first organic solvent is an alkylbenzoate according to general formula (I) wherein

-   R¹ is a straight-chain alkyl group having from 1 to 20 carbon atoms    or a branched or cyclic alkyl group having from 3 to 20 carbon    atoms, in which one or more non-adjacent CH₂ groups may be replaced    by —O—, —S—, —CO—O—, —C═O—, —CH═CH— or —C≡C—, and in which one or    more hydrogen atoms may be replaced by F, or an aryl or heteroaryl    group which has from 4 to 14 carbon atoms and may be substituted by    one or more nonaromatic R³ radicals,-   R² is a straight-chain alkyl group having from 1 to 20 carbon atoms    or a branched or cyclic alkyl group having from 3 to 20 carbon    atoms, and-   n is 0 or 1, preferably 0.

In a most preferred embodiment, the first organic solvent is an alkylbenzoate according to general formula (I) wherein

-   R² is a straight-chain alkyl group having from 1 to 4 carbon atoms,    preferably 4 carbon atoms, and-   n is 0.

According to the most preferred embodiment, the first solvent isn-butyl-benzoate according to formula (II)

Examples of preferred alkyl benzoates and their boiling points (BP) areshown in the following Table 1.

TABLE 1 Preferred alkyl benzoates and their boiling points (BP). BP (°C.) Substance at 1atm

198

214

211

250

Preferably, the first solvent has a surface tension of ≥20 mN/m. Morepreferably, the surface tension of the first solvent is in the rangefrom 25 to 40 mN/m and most preferably in the range from 28 to 37.5mN/m.

The content of the first solvent is in the range from 50 to 100 vol.-%,preferably in the range from 75 to 100 vol.-%, more preferably in therange from 90 to 100 vol.-%, and most preferably 100 vol.-%, based onthe total amount of solvents in the formulation.

Consequently, the content of the second solvent is in the range from 0to 50 vol.-%, preferably in the range from 0 to 25 vol.-% and morepreferably in the range from 0 to 10 vol.-%, based on the total amountof solvents in the formulation. Most preferably, the formulation of thepresent application does not contain a second solvent.

Preferably, the first solvent has a boiling point in the range from 100to 400° C., more preferably in the range from 150 to 350° C.

The formulations according to the present invention comprise in onepreferred embodiment at least a second solvent which is different fromthe first solvent. The second solvent is employed together with thefirst solvent.

In one embodiment, the second solvent could also be an alkyl benzoate,which is different from the first solvent. Nevertheless, preferably, thesecond solvent is not an alkyl benzoate.

Suitable second solvents are preferably organic solvents which includeinter alia, alcohols, aldehydes, ketones, ethers, esters, amides such asdi-C₁₋₂-alkylformamides, sulfur compounds, nitro compounds,hydrocarbons, halogenated hydrocarbons (e.g. chlorinated hydrocarbons),aromatic or heteroaromatic hydrocarbons and halogenated aromatic orheteroaromatic hydrocarbons.

Preferably, the second solvent can be chosen from one of the followinggroups: substituted and non-substituted aromatic or linear ethers suchas 3-phenoxytoluene or anisole; substituted or non-substituted arenederivatives such as xylene; indane derivatives such as hexamethylindane;substituted and non-substituted aromatic or linear ketones; substitutedand non-substituted heterocycles such as pyrrolidinones, pyridines,pyrazines; other fluorinated or chlorinated aromatic hydrocarbons.

Particularly preferred second organic solvents are, for example,1,2,3,4-tetramethylbenzene, 1,2,3,5-tetramethylbenzene,1,2,3-trimethylbenzene, 1,2,4,5-tetramethylbenzene,1,2,4-trichlorobenzene, 1,2,4-trimethyl-benzene, 1,2-dihydronaphthalene,1,2-dimethylnaphthalene, 1,3-benzo-dioxolane, 1,3-diisopropylbenzene,1,3-dimethylnaphthalene, 1,4-benzo-dioxane, 1,4-diisopropylbenzene,1,4-dimethylnaphthalene, 1,5-dimethyl-tetralin, 1-benzothiophene,thianaphthalene, 1-bromonaphthalene, 1-chloro-methylnaphthalene,1-ethylnaphthalene, 1-methoxynaphthalene, 1-methylnaphthalene,1-methylindole, 2,3-benzofuran, 2,3-dihydrobenzo-furan,2,3-dimethylanisole, 2,4-dimethylanisole, 2,5-dimethylanisole,2,6-dimethylanisole, 2,6-dimethylnaphthalene,2-bromo-3-bromomethylnaphthalene, 2-bromomethylnaphthalene,2-bromonaphthalene, 2-ethoxynaphthalene, 2-ethylnaphthalene,2-isopropylanisole, 2-methylanisole, 2-methyl-indole,3,4-dimethylanisole, 3,5-dimethylanisole, 3-bromoquinoline,3-methylanisole, 4-methylanisole, 5-decanolide, 5-methoxyindane,5-methoxyindole, 5-tert-butyl-m-xylene, 6-methylquinoline,8-methylquinoline, acetophenone, anisole, benzonitrile, benzothiazole,benzyl acetate, bromobenzene, butyl phenyl ether, cyclohexylbenzene,decahydronaphthol, dimethoxytoluene, 3-phenoxytoluene, diphenyl ether,propiophenone, ethylbenzene, hexylbenzene, indane, hexamethylindane,indene, isochroman, cumene, m-cymene, mesitylene, o-, m-, p-xylene,propylbenzene, o-dichlorobenzene, pentylbenzene, phenetol,ethoxybenzene, phenyl acetate, p-cymene, propiophenone,sec-butylbenzene, t-butylbenzene, thiophene, toluene, veratrol,monochlorobenzene, o-dichlorobenzene, pyridine, pyrazine, pyrimidine,pyrrolidinone, morpholine, dimethylacetamide, dimethyl sulfoxide,decalin and/or mixtures of these compounds.

These solvents can be employed individually or as a mixture of two,three or more solvents forming the second solvent.

Preferably, the second solvent has a boiling point in the range from 100to 400° C., more preferably in the range from 150 to 350° C.

The at least one organic functional material has a solubility in thefirst as well as in the second solvent which is preferably in the rangefrom 1 to 250 g/l and more preferably in the range from 1 to 50 g/l.

The content of the at least one organic functional material in theformulation is in the range from 0.001 to 20 weight-%, preferably in therange from 0.01 to 10 weight-%, more preferably in the range from 0.1 to5 weight-% and most preferably in the range from 0.3 to 5 weight-%,based on the total weight of the formulation.

The formulation according to the present invention has a surface tensionpreferably in the range from 15 to 80 mN/m, more preferably in the rangefrom 20 to 60 mN/m and most preferably in the range from 25 to 40 mN/m.

Furthermore, the formulation according to the present invention has aviscosity preferably in the range from 1 to 50 mPa·s, more preferably inthe range from 2 to 40 mPa·s, and most preferably in the range from 2 to20 mPa·s.

Preferably, the organic solvent blend comprises a surface tension in therange from 15 to 80 mN/m, more preferably in the range from 20 to 60mN/m and most preferably in the range from 25 to 40 mN/m. The surfacetension can be measured using a FTA (First Ten Angstrom) 1000 contactangle goniometer at 20° C. Details of the method are available fromFirst Ten Angstrom as published by Roger P. Woodward, Ph.D. “SurfaceTension Measurements Using the Drop Shape Method”. Preferably, thependant drop method can be used to determine the surface tension. Thismeasurement technique dispenses a drop from a needle in a bulk liquid orgaseous phase. The shape of the drop results from the relationshipbetween the surface-tension, gravity and density differences. Using thependant drop method, the surface tension is calculated from the shadowimage of a pendant drop usinghttp://www.kruss.de/services/education-theory/glossary/drop-shape-analysis.A commonly used and commercially available high precision drop shapeanalysis tool, namely DSA100 from Krüss, was used to perform all surfacetension measure-ments. The surface tension is determined by the softwareDSA4. All measurements were performed at room temperature which is inthe range between 20° C. and 25° C. The standard operating procedureincludes the determination of the surface tension of each formulationusing a fresh disposable drop dispensing system (syringe and needle).Each drop is measured over the duration of one minute with sixtymeasurements which are later on averaged. For each formulation threedrops are measured. The final value is averaged over said measurements.The tool is regularly cross-checked against various liquids having wellknown surface tensions.

The viscosity of the formulations and solvents according to the presentinvention is measured with a 1° cone-plate rotational rheometer of thetype Haake Mars III (Thermo Scientific). The equipment allows a precisecontrol of the temperature and sheer rate. The measurement of theviscosity is carried out at a temperature of 25.0° C. (+/−0.2° C.) and asheer rate of 500 s⁻¹. Each sample is measured three times and theobtained measured values are averaged.

The formulation according to the present invention comprises at leastone organic functional material which can be employed for the productionof functional layers of electronic devices. Functional materials aregenerally the organic materials which are introduced between the anodeand the cathode of an electronic device.

The term organic functional material denotes, inter alia, organicconductors, organic semiconductors, organic fluorescent compounds,organic phosphorescent compounds, organic light-absorbent compounds,organic light-sensitive compounds, organic photosensitisation agents andother organic photoactive compounds. The term organic functionalmaterial furthermore encompasses organometallic complexes of transitionmetals, rare earths, lanthanides and actinides.

The organic functional material is selected from the group consisting offluorescent emitters, phosphorescent emitters, host materials, matrixmaterials, exciton-blocking materials, electron-transport materials,electron-injection materials, hole-conductor materials, hole-injectionmaterials, n-dopants, p-dopants, wide-band-gap materials,electron-blocking materials and hole-blocking materials.

Preferred embodiments of organic functional materials are disclosed indetail in WO 2011/076314 A1, where this document is incorporated intothe present application by way of reference.

In a preferred embodiment, the organic functional material is an organicsemiconductor selected from the group consisting of hole-injecting,hole-transporting, emitting, electron-transporting andelectron-injecting materials.

The organic functional material can be a compound having a low molecularweight, a polymer, an oligomer or a dendrimer, where the organicfunctional material may also be in the form of a mixture. Thus, theformulations according to the present invention may comprise two or moredifferent compounds having a low molecular weight, one compound having alow molecular weight and one polymer or two polymers (blend).

Organic functional materials are frequently described via the propertiesof the frontier orbitals, which are described in greater detail below.Molecular orbitals, in particular also the highest occupied molecularorbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), theirenergy levels and the energy of the lowest triplet state T₁ or of thelowest excited singlet state S₁ of the materials can be estimated basedon quantum-chemical calculations. In order to calculate these propertiesfor organic substances without metals, firstly a geometry optimisationis carried out using the “Ground State/Semi-empirical/DefaultSpin/AM1/Charge 0/Spin Singlet” method. An energy calculation issubsequently carried out on the basis of the optimised geometry. The“TD-SCF/DFT/Default Spin/B3PW91” method with the “6-31G(d)” base set(charge 0, spin singlet) is used here. For metal-containing compounds,the geometry is optimised via the “Ground State/Hartree-Fock/DefaultSpin/LanL2 MB/Charge 0/Spin Singlet” method. The energy calculation iscarried out analogously to the above-described method for the organicsubstances, with the difference that the “LanL2DZ” base set is used forthe metal atom and the “6-31G(d)” base set is used for the ligands. Theenergy calculation gives the HOMO energy level HEh or LUMO energy levelLEh in hartree units. The HOMO and LUMO energy levels in electron voltscalibrated with reference to cyclic voltammetry measurements aredetermined therefrom as follows:

HOMO(eV)=((HEh*27.212)-0.9899)/1.1206

LUMO(eV)=((LEh*27.212)-2.0041)/1.385

For the purposes of the present application, these values are to beregarded as HOMO and LUMO energy levels respectively of the materials.

The lowest triplet state T₁ is defined as the energy of the tripletstate having the lowest energy which arises from the quantum-chemicalcalculation described.

The lowest excited singlet state S₁ is defined as the energy of theexcited singlet state having the lowest energy which arises from thequantum-chemical calculation described.

The method described herein is independent of the software package usedand always gives the same results. Examples of frequently used programsfor this purpose are “Gaussian09 W” (Gaussian Inc.) and Q-Chem 4.1(Q-Chem, Inc.).

Compounds having hole-injection properties, also called hole-injectionmaterials herein, simplify or facilitate the transfer of holes, i.e.positive charges, from the anode into an organic layer. In general, ahole-injection material has an HOMO level which is in the region of orabove the level of the anode, i.e. in general is at least −5.3 eV.

Compounds having hole-transport properties, also called hole-transportmaterials herein, are capable of transporting holes, i.e. positivecharges, which are generally injected from the anode or an adjacentlayer, for example a hole-injection layer. A hole-transport materialgenerally has a high HOMO level of preferably at least −5.4 eV.Depending on the structure of an electronic device, it may also bepossible to employ a hole-transport material as hole-injection material.

The preferred compounds which have hole-injection and/or hole-transportproperties include, for example, triarylamines, benzidines,tetraaryl-para-phenylenediamines, triarylphosphines, phenothiazines,phenoxazines, dihydrophenazines, thianthrenes, dibenzo-para-dioxins,phenoxathiynes, carbazoles, azulenes, thiophenes, pyrroles and furans aswell as their derivatives and further O-, S- or N-containingheterocycles having a high HOMO (HOMO=highest occupied molecularorbital).

As compounds which have hole-injection and/or hole-transport properties,particular mention may be made of phenylenediamine derivatives (U.S.Pat. No. 3,615,404), arylamine derivatives (U.S. Pat. No. 3,567,450),amino-substituted chalcone derivatives (U.S. Pat. No. 3,526,501),styrylanthracene derivatives (JP-A-56-46234), polycyclic aromaticcompounds (EP 1009041), polyarylalkane derivatives (U.S. Pat. No.3,615,402), fluorenone derivatives (JP-A-54-110837), hydrazonederivatives (U.S. Pat. No. 3,717,462), acylhydrazones, stilbenederivatives (JP-A61-210363), silazane derivatives (U.S. Pat. No.4,950,950), polysilanes (JP-A-2-204996), aniline copolymers(JP-A-2-282263), thiophene oligomers (JP Heisei 1 (1989) 211399),polythiophenes, poly(N-vinylcarbazole) (PVK), polypyrroles, polyanilinesand other electrically conducting macromolecules, porphyrin compounds(JP-A-63-2956965, U.S. Pat. No. 4,720,432), aromatic dimethylidene-typecompounds, carbazole compounds, such as, for example, CDBP, CBP, mCP,aromatic tertiary amine and styrylamine compounds (U.S. Pat. No.4,127,412), such as, for example, triphenylamines of the benzidine type,triphenylamines of the styrylamine type and triphenylamines of thediamine type. It is also possible to use arylamine dendrimers (JP Heisei8 (1996) 193191), monomeric triarylamines (U.S. Pat. No. 3,180,730),triarylamines containing one or more vinyl radicals and/or at least onefunctional group containing active hydrogen (U.S. Pat. Nos. 3,567,450and 3,658,520), or tetraaryldiamines (the two tertiary amine units areconnected via an aryl group). More triarylamino groups may also bepresent in the molecule. Phthalocyanine derivatives, naphthalocyaninederivatives, butadiene derivatives and quinoline derivatives, such as,for example, dipyrazino[2,3-f:2′,3′-h]quinoxalinehexacarbonitrile, arealso suitable.

Preference is given to aromatic tertiary amines containing at least twotertiary amine units (US 2008/0102311 A1, U.S. Pat. Nos. 4,720,432 and5,061,569), such as, for example, NPD(α-NPD=4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl) (U.S. Pat. No.5,061,569), TPD 232(═N,N′-bis-(N,N′-diphenyl-4-aminophenyl)-N,N-diphenyl-4,4′-diamino-1,1′-biphenyl)or MTDATA (MTDATA orm-MTDATA=4,4′,4″-tris[3-methylphenyl)phenylamino]-triphenylamine)(JP-A-4-308688), TBDB (═N,N,N′,N′-tetra(4-biphenyl)-diaminobiphenylene),TAPC(=1,1-bis(4-di-p-tolylaminophenyl)cyclohexane), TAPPP(=1,1-bis(4-di-p-tolylaminophenyl)-3-phenylpropane), BDTAPVB(=1,4-bis[2-[4-[N,N-di(p-tolyl)amino]phenyl]vinyl]benzene), TTB(═N,N,N′,N′-tetra-p-tolyl-4,4′-diaminobiphenyl), TPD(=4,4′-bis[N-3-methylphenyl]-N-phenylamino)biphenyl),N,N,N′,N′-tetraphenyl-4,4′″-diamino-1,1′,4′,1″,4″,1′″-quaterphenyl,likewise tertiary amines containing carbazole units, such as, forexample, TCTA(=4-(9H-carbazol-9-yl)-N,N-bis[4-(9H-carbazol-9-yl)phenyl]benzenamine).Preference is likewise given to hexaazatriphenylene compounds inaccordance with US 2007/0092755 A1 and phthalocyanine derivatives (forexample H₂Pc, CuPc (=copper phthalocyanine), CoPc, NiPc, ZnPc, PdPc,FePc, MnPc, ClAlPc, ClGaPc, ClInPc, ClSnPc, Cl₂SiPc, (HO)AlPc, (HO)GaPc,VOPc, TiOPc, MoOPc, GaPc-O—GaPc).

Particular preference is given to the following triarylamine compoundsof the formulae (TA-1) to (TA-12), which are disclosed in EP 1162193 B1,EP 650 955 B1, Synth. Metals 1997, 91(1-3), 209, DE 19646119 A1, WO2006/122630 A1, EP 1 860 097 A1, EP 1834945 A1, JP 08053397 A, U.S. Pat.No. 6,251,531 B1, US 2005/0221124, JP 08292586 A, U.S. Pat. No.7,399,537 B2, US 2006/0061265 A1, EP 1 661 888 and WO 2009/041635. Thesaid compounds of the formulae (TA-1) to (TA-12) may also besubstituted:

Further compounds which can be employed as hole-injection materials aredescribed in EP 0891121 A1 and EP 1029909 A1, injection layers ingeneral in US 2004/0174116 A1.

These arylamines and heterocycles which are generally employed ashole-injection and/or hole-transport materials preferably result in anHOMO in the polymer of greater than −5.8 eV (vs. vacuum level),particularly preferably greater than −5.5 eV.

Compounds which have electron-injection and/or electron-transportproperties are, for example, pyridines, pyrimidines, pyridazines,pyrazines, oxadiazoles, quinolines, quinoxalines, anthracenes,benzanthracenes, pyrenes, perylenes, benzimidazoles, triazines, ketones,phosphine oxides and phenazines and derivatives thereof, but alsotriarylboranes and further O-, S- or N-containing heterocycles having alow LUMO (LUMO=lowest unoccupied molecular orbital).

Particularly suitable compounds for electron-transporting andelectron-injecting layers are metal chelates of 8-hydroxyquinoline (forexample LiQ, AlQ₃, GaQ₃, MgQ₂, ZnQ₂, InQ₃, ZrQ₄), BAlQ, Ga oxinoidcomplexes, 4-azaphenanthren-5-ol-Be complexes (U.S. Pat. No. 5,529,853A, cf. formula ET-1), butadiene derivatives (U.S. Pat. No. 4,356,429),heterocyclic optical brighteners (U.S. Pat. No. 4,539,507),benzimidazole derivatives (US 2007/0273272 A1), such as, for example,TPBI (U.S. Pat. No. 5,766,779, cf. formula ET-2), 1,3,5-triazines, forexample spirobifluorenyltriazine derivatives (for example in accordancewith DE 102008064200), pyrenes, anthracenes, tetracenes, fluorenes,spirofluorenes, dendrimers, tetracenes (for example rubrenederivatives), 1,10-phenanthroline derivatives (JP 2003-115387, JP2004-311184, JP 2001-267080, WO 02/043449), silacyclopentadienederivatives (EP 1480280, EP 1478032, EP 1469533), borane derivatives,such as, for example, triarylborane derivatives containing Si (US2007/0087219 A1, cf. formula ET3), pyridine derivatives (JP2004-200162), phenanthrolines, especially 1,10-phenanthrolinederivatives, such as, for example, BCP and Bphen, also severalphenanthrolines connected via biphenyl or other aromatic groups (US2007-0252517 A1) or phenanthrolines connected to anthracene (US2007-0122656 A1, cf. formulae ET-4 and ET-5).

Likewise suitable are heterocyclic organic compounds, such as, forexample, thiopyran dioxides, oxazoles, triazoles, imidazoles oroxadiazoles. Examples of the use of five-membered rings containing N,such as, for example, oxazoles, preferably 1,3,4-oxadiazoles, forexample compounds of the formulae ET-6, ET-7, ET-8 and ET-9, which aredisclosed, inter alia, in US 2007/0273272 A1; thiazoles, oxadiazoles,thiadiazoles, triazoles, inter alia, see US 2008/0102311 A1 and Y. A.Levin, M. S. Skorobogatova, Khimiya Geterotsiklicheskikh Soedinenii 1967(2), 339-341, preferably compounds of the formula ET-10,silacyclopentadiene derivatives. Preferred compounds are the followingof the formulae (ET-6) to (ET-10):

It is also possible to employ organic compounds, such as fluorenones,fluorenylidenemethanes, perylenetetracarbonic acids,anthraquinonedimethanes, diphenoquinones, anthrones andanthraquinonediethylenediamines and derivatives thereof.

Preference is given to 2,9,10-substituted anthracenes (with 1- or2-naphthyl and 4- or 3-biphenyl) or molecules which contain twoanthracene units (US 2008/0193796 A1, cf. formula ET-11). Also veryadvantageous is the connection of 9,10-substituted anthracene units tobenzimidazole derivatives (US 2006/147747 A and EP 1551206 A1, cf.formulae ET-12 and ET-13).

The compounds which are able to generate electron-injection and/orelectron-transport properties preferably result in an LUMO of less than−2.5 eV (vs. vacuum level), particularly preferably less than −2.7 eV.

The present formulations may comprise emitters. The term emitter denotesa material which, after excitation, which can take place by transfer ofany type of energy, allows a radiative transition into a ground statewith emission of light. In general, two classes of emitter are known,namely fluorescent and phosphorescent emitters. The term fluorescentemitter denotes materials or compounds in which a radiative transitionfrom an excited singlet state into the ground state takes place. Theterm phosphorescent emitter preferably denotes luminescent materials orcompounds which contain transition metals.

Emitters are frequently also called dopants if the dopants cause theproperties described above in a system. A dopant in a system comprisinga matrix material and a dopant is taken to mean the component whoseproportion in the mixture is the smaller. Correspondingly, a matrixmaterial in a system comprising a matrix material and a dopant is takento mean the component whose proportion in the mixture is the greater.Accordingly, the term phosphorescent emitter can also be taken to mean,for example, phosphorescent dopant.

Compounds which are able to emit light include, inter alia, fluorescentemitters and phosphorescent emitters. These include, inter alia,compounds containing stilbene, stilbenamine, styrylamine, coumarine,rubrene, rhodamine, thiazole, thiadiazole, cyanine, thiophene,paraphenylene, perylene, phtalocyanine, porphyrin, ketone, quinoline,imine, anthracene and/or pyrene structures. Particular preference isgiven to compounds which are able to emit light from the triplet statewith high efficiency, even at room temperature, i.e. exhibitelectrophosphorescence instead of electrofluorescence, which frequentlycauses an increase in the energy efficiency. Suitable for this purposeare firstly compounds which contain heavy atoms having an atomic numberof greater than 36. Preference is given to compounds which contain d- orf-transition metals which satisfy the above-mentioned condition.Particular preference is given here to corresponding compounds whichcontain elements from group 8 to 10 (Ru, Os, Rh, Ir, Pd, Pt). Suitablefunctional compounds here are, for example, various complexes, asdescribed, for example, in WO 02/068435 A1, WO 02/081488 A1, EP 1239526A2 and WO 2004/026886 A2.

Preferred compounds which can serve as fluorescent emitters aredescribed by way of example below. Preferred fluorescent emitters areselected from the class of the monostyrylamines, the distyrylamines, thetristyrylamines, the tetrastyrylamines, the styrylphosphines, the styrylethers and the arylamines.

A monostyrylamine is taken to mean a compound which contains onesubstituted or unsubstituted styryl group and at least one, preferablyaromatic, amine. A distyrylamine is taken to mean a compound whichcontains two substituted or unsubstituted styryl groups and at leastone, preferably aromatic, amine. A tristyrylamine is taken to mean acompound which contains three substituted or unsubstituted styryl groupsand at least one, preferably aromatic, amine. A tetrastyrylamine istaken to mean a compound which contains four substituted orunsubstituted styryl groups and at least one, preferably aromatic,amine. The styryl groups are particularly preferably stilbenes, whichmay also be further substituted. Corresponding phosphines and ethers aredefined analogously to the amines. An arylamine or an aromatic amine inthe sense of the present invention is taken to mean a compound whichcontains three substituted or unsubstituted aromatic or heteroaromaticring systems bonded directly to the nitrogen. At least one of thesearomatic or heteroaromatic ring systems is preferably a condensed ringsystem, preferably having at least 14 aromatic ring atoms. Preferredexamples thereof are aromatic anthracenamines, aromaticanthracenediamines, aromatic pyrenamines, aromatic pyrenediamines,aromatic chrysenamines or aromatic chrysenediamines. An aromaticanthracenamine is taken to mean a compound in which one diarylaminogroup is bonded directly to an anthracene group, preferably in the9-position. An aromatic anthracenediamine is taken to mean a compound inwhich two diarylamino groups are bonded directly to an anthracene group,preferably in the 2,6- or 9,10-position. Aromatic pyrenamines,pyrenediamines, chrysenamines and chrysenediamines are definedanalogously thereto, where the diarylamino groups are preferably bondedto the pyrene in the 1-position or in the 1,6-position.

Further preferred fluorescent emitters are selected fromindenofluoren-amines or indenofluorenediamines, which are described,inter alia, in WO 2006/122630; benzoindenofluorenamines orbenzoindenofluorenediamines, which are described, inter alia, in WO2008/006449; and dibenzoindenofluorenamines ordibenzoindenofluorenediamines, which are described, inter alia, in WO2007/140847.

Examples of compounds from the class of the styrylamines which can beemployed as fluorescent emitters are substituted or unsubstitutedtristilbenamines or the dopants described in WO 2006/000388, WO2006/058737, WO 2006/000389, WO 2007/065549 and WO 2007/115610.Distyryl-benzene and distyrylbiphenyl derivatives are described in U.S.Pat. No. 5,121,029. Further styrylamines can be found in US 2007/0122656A1.

Particularly preferred styrylamine compounds are the compounds of theformula EM-1 described in U.S. Pat. No. 7,250,532 B2 and the compoundsof the formula EM-2 described in DE 10 2005 058557 A1:

Particularly preferred triarylamine compounds are compounds of theformulae EM-3 to EM-15 disclosed in CN 1583691 A, JP 08/053397 A andU.S. Pat. No. 6,251,531 B1, EP 1957606 A1, US 2008/0113101 A1, US2006/210830 A, WO 2008/006449 and DE 102008035413 and derivativesthereof:

Further preferred compounds which can be employed as fluorescentemitters are selected from derivatives of naphthalene, anthracene,tetracene, benzanthracene, benzophenanthrene (DE 10 2009 005746),fluorene, fluoranthene, periflanthene, indenoperylene, phenanthrene,perylene (US 2007/0252517 A1), pyrene, chrysene, decacyclene, coronene,tetraphenylcyclopentadiene, pentaphenylcyclopentadiene, fluorene,spirofluorene, rubrene, coumarine (U.S. Pat. Nos. 4,769,292, 6,020,078,US 2007/0252517 A1), pyran, oxazole, benzoxazole, benzothiazole,benzimidazole, pyrazine, cinnamic acid esters, diketopyrrolopyrrole,acridone and quinacridone (US 2007/0252517 A1).

Of the anthracene compounds, particular preference is given to9,10-substituted anthracenes, such as, for example,9,10-diphenylanthracene and 9,10-bis(phenylethynyl)anthracene.1,4-Bis(9′-ethynylanthracenyl)benzene is also a preferred dopant.

Preference is likewise given to derivatives of rubrene, coumarine,rhodamine, quinacridone, such as, for example, DMQA(═N,N′-dimethylquinacridone), dicyanomethylenepyran, such as, forexample, DCM(=4-(dicyanoethylene)-6-(4-dimethylaminostyryl-2-methyl)-4H-pyran),thiopyran, polymethine, pyrylium and thiapyrylium salts, periflantheneand indenoperylene.

Blue fluorescent emitters are preferably polyaromatic compounds, suchas, for example, 9,10-di(2-naphthylanthracene) and other anthracenederivatives, derivatives of tetracene, xanthene, perylene, such as, forexample, 2,5,8,11-tetra-t-butylperylene, phenylene, for example4,4′-bis(9-ethyl-3-carbazovinylene)-1,1′-biphenyl, fluorene,fluoranthene, arylpyrenes (US 2006/0222886 A1), arylenevinylenes (U.S.Pat. Nos. 5,121,029, 5,130,603), bis(azinyl)imine-boron compounds (US2007/0092753 A1), bis(azinyl)methene compounds and carbostyrylcompounds.

Further preferred blue fluorescent emitters are described in C. H. Chenet al.: “Recent developments in organic electroluminescent materials”Macromol. Symp. 125, (1997) 1-48 and “Recent progress of molecularorganic electroluminescent materials and devices” Mat. Sci. and Eng. R,39 (2002), 143-222.

Further preferred blue-fluorescent emitters are the hydrocarbonsdisclosed in DE 102008035413.

Preferred compounds which can serve as phosphorescent emitters aredescribed below by way of example.

Examples of phosphorescent emitters are revealed by WO 00/70655, WO01/41512, WO 02/02714, WO 02/15645, EP 1191613, EP 1191612, EP 1191614and WO 2005/033244. In general, all phosphorescent complexes as are usedin accordance with the prior art for phosphorescent OLEDs and as areknown to the person skilled in the art in the area of organicelectroluminescence are suitable, and the person skilled in the art willbe able to use further phosphorescent complexes without inventive step.

Phosphorescent metal complexes preferably contain Ir, Ru, Pd, Pt, Os orRe, more preferably Ir.

Preferred ligands are 2-phenylpyridine derivatives, 7,8-benzoquinolinederivatives, 2-(2-thienyl)pyridine derivatives, 2-(1-naphthyl)pyridinederivatives, 1-phenylisoquinoline derivatives, 3-phenylisoquinolinederivatives or 2-phenylquinoline derivatives. All these compounds may besubstituted, for example by fluoro, cyano and/or trifluoromethylsubstituents for blue. Auxiliary ligands are preferably acetylacetonateor picolinic acid.

In particular, complexes of Pt or Pd with tetradentate ligands of theformula EM-16 are suitable

The compounds of the formula EM-16 are described in greater detail in US2007/0087219 A1, where, for an explanation of the substituents andindices in the above formula, reference is made to this specificationfor disclosure purposes. Furthermore, Pt-porphyrin complexes having anenlarged ring system (US 2009/0061681 A1) and Ir complexes, for example2,3,7,8,12,13,17,18-octaethyl-21H, 23H-porphyrin-Pt(II),tetraphenyl-Pt(II) tetrabenzoporphyrin (US 2009/0061681 A1),cis-bis(2-phenylpyridinatoN,C²′)Pt(II),cis-bis(2-(2′-thienyl)pyridinato-N,C³′)Pt(II),cis-bis(2-(2′-thienyl)quinolinato-N,C⁵′)Pt(II),(2-(4,6-difluorophenyl)pyridinato-N,C²′)Pt(II) (acetylacetonate), ortris(2-phenylpyridinato-N,C²′)Ir(III) (═Ir(ppy)₃, green),bis(2-phenylpyridinato-N,C²)Ir(III) (acetylacetonate) (═Ir(ppy)₂acetylacetonate, green, US 2001/0053462 A1, Baldo, Thompson et al.Nature 403, (2000), 750-753),bis(1-phenylisoquinolinato-N,C²′)(2-phenylpyridinato-N,C²′)iridium(III),bis(2-phenylpyridinato-N,C²′)(1-phenylisoquinolinato-N,C²′)iridium(III),bis(2-(2′-benzothienyl)pyridinato-N,C³′)iridium(III) (acetylacetonate),bis(2-(4′,6′-difluorophenyl)pyridinato-N,C²′)iridium(III) (piccolinate)(Firpic, blue), bis(2-(4′,6′-difluorophenyl)pyridinato-N,C²′)Ir(III)(tetrakis(1-pyrazolyl)borate),tris(2-(biphenyl-3-yl)-4-tert-butylpyridine)iridium(III),(ppz)₂Ir(5phdpym) (US 2009/0061681 A1), (45ooppz)₂-Ir(5phdpym) (US2009/0061681 A1), derivatives of 2-phenylpyridine-Ir complexes, such as,for example, PQIr (=iridium(III)bis(2-phenylquinolylN,C²′)acetylacetonate),tris(2-phenylisoquinolinato-N,C)Ir(III) (red),bis(2-(2′-benzo[4,5-a]thienyl)pyridinato-N,C³)Ir (acetylacetonate)([Btp₂Ir(acac)], red, Adachi et al. Appl. Phys. Lett. 78 (2001),1622-1624).

Likewise suitable are complexes of trivalent lanthanides, such as, forexample, Tb³⁺ and Eu³⁺ (J. Kido et al. Appl. Phys. Lett. 65 (1994),2124, Kido et al. Chem. Lett. 657, 1990, US 2007/0252517 A1), orphosphorescent complexes of Pt(II), Ir(I), Rh(I) with maleonitriledithiolate (Johnson et al., JACS 105, 1983, 1795), Re(I)tricarbonyl-diimine complexes (Wrighton, JACS 96, 1974, 998, interalia), Os(II) complexes with cyano ligands and bipyridyl orphenanthroline ligands (Ma et al., Synth. Metals 94, 1998, 245).

Further phosphorescent emitters having tridentate ligands are describedin U.S. Pat. No. 6,824,895 and U.S. Ser. No. 10/729,238. Red-emittingphosphorescent complexes are found in U.S. Pat. Nos. 6,835,469 and6,830,828.

Particularly preferred compounds which are used as phosphorescentdopants are, inter alia, the compounds of the formula EM-17 described,inter alia, in US 2001/0053462 A1 and Inorg. Chem. 2001, 40(7),1704-1711, JACS 2001, 123(18), 4304-4312, and derivatives thereof.

Derivatives are described in U.S. Pat. No. 7,378,162 B2, U.S. Pat. No.6,835,469 B2 and JP 2003/253145 A.

Furthermore, the compounds of the formulae EM-18 to EM-21 described inU.S. Pat. No. 7,238,437 B2, US 2009/008607 A1 and EP 1348711, andderivatives thereof, can be employed as emitters.

Quantum dots can likewise be employed as emitters, these materials beingdisclosed in detail in WO 2011/076314 A1.

Compounds which are employed as host materials, in particular togetherwith emitting compounds, include materials from various classes ofsubstances.

Host materials generally have larger band gaps between HOMO and LUMOthan the emitter materials employed. In addition, preferred hostmaterials exhibit properties of either a hole- or electron-transportmaterial. Furthermore, host materials can have both electron- andhole-transport properties.

Host materials are in some cases also called matrix material, inparticular if the host material is employed in combination with aphosphorescent emitter in an OLED.

Preferred host materials or co-host materials, which are employed, inparticular, together with fluorescent dopants, are selected from theclasses of the oligoarylenes (for example2,2′,7,7′-tetraphenylspirobifluorene in accordance with EP 676461 ordinaphthylanthracene), in particular the oligoarylenes containingcondensed aromatic groups, such as, for example, anthracene,benzanthracene, benzophenanthrene (DE 10 2009 005746, WO 2009/069566),phenanthrene, tetracene, coronene, chrysene, fluorene, spirofluorene,perylene, phthaloperylene, naphthaloperylene, decacyclene, rubrene, theoligoarylenevinylenes (for exampleDPVBi=4,4′-bis(2,2-diphenylethenyl)-1,1′-biphenyl or spiro-DPVBi inaccordance with EP 676461), the polypodal metal complexes (for examplein accordance with WO 04/081017), in particular metal complexes of8-hydroxyquinoline, for example AlQ₃ (=aluminium(III)tris(8-hydroxyquinoline)) orbis(2-methyl-8-quinolinolato)-4-(phenylphenolinolato)aluminium, alsowith imidazole chelate (US 2007/0092753 A1) and the quinoline-metalcomplexes, aminoquinoline-metal complexes, benzoquinoline-metalcomplexes, the hole-conducting compounds (for example in accordance withWO 2004/058911), the electron-conducting compounds, in particularketones, phosphine oxides, sulfoxides, etc. (for example in accordancewith WO 2005/084081 and WO 2005/084082), the atropisomers (for examplein accordance with WO 2006/048268), the boronic acid derivatives (forexample in accordance with WO 2006/117052) or the benzanthracenes (forexample in accordance with WO 2008/145239).

Particularly preferred compounds which can serve as host materials orco-host materials are selected from the classes of the oligoarylenes,comprising anthracene, benzanthracene and/or pyrene, or atropisomers ofthese compounds. An oligoarylene in the sense of the present inventionis intended to be taken to mean a compound in which at least three arylor arylene groups are bonded to one another.

Preferred host materials are selected, in particular, from compounds ofthe formula (H-1),

Ar⁴—(Ar⁵)_(p)—Ar⁶  (H-1)

where Ar⁴, Ar⁵, Ar⁶ are on each occurrence, identically or differently,an aryl or heteroaryl group having 5 to 30 aromatic ring atoms, whichmay optionally be substituted, and p represents an integer in the rangefrom 1 to 5; the sum of the π electrons in Ar⁴, Ar⁵ and Ar⁶ is at least30 if p=1 and at least 36 if p=2 and at least 42 if p=3.

In the compounds of the formula (H-1), the group Ar⁵ particularlypreferably stands for anthracene, and the groups Ar⁴ and Ar⁶ are bondedin the 9- and 10-position, where these groups may optionally besubstituted. Very particularly preferably, at least one of the groupsAr⁴ and/or Ar⁶ is a condensed aryl group selected from 1- or 2-naphthyl,2-, 3- or 9-phenanthrenyl or 2-, 3-, 4-, 5-, 6- or 7-benzanthracenyl.Anthracene-based compounds are described in US 2007/0092753 A1 and US2007/0252517 A1, for example2-(4-methylphenyl)-9,10-di-(2-naphthyl)anthracene,9-(2-naphthyl)-10-(1,1′-biphenyl)anthracene and9,10-bis[4-(2,2-diphenylethenyl)phenyl]anthracene,9,10-diphenylanthracene, 9,10-bis(phenylethynyl)anthracene and1,4-bis(9′-ethynylanthracenyl)benzene. Preference is also given tocompounds containing two anthracene units (US 2008/0193796 A1), forexample 10,10′-bis[1,1′,4′,1″]terphenyl-2-yl-9,9′-bisanthracenyl.

Further preferred compounds are derivatives of arylamine, styrylamine,fluorescein, diphenylbutadiene, tetraphenylbutadiene, cyclopentadiene,tetraphenylcyclopentadiene, pentaphenylcyclopentadiene, coumarine,oxadiazole, bisbenzoxazoline, oxazole, pyridine, pyrazine, imine,benzothiazole, benzoxazole, benzimidazole (US 2007/0092753 A1), forexample 2,2′,2″-(1,3,5-phenylene)tris[1-phenyl-1H-benzimidazole],aldazine, stilbene, styrylarylene derivatives, for example9,10-bis[4-(2,2-diphenylethenyl)phenyl]anthracene, and distyrylarylenederivatives (U.S. Pat. No. 5,121,029), diphenylethylene,vinylanthracene, diaminocarbazole, pyran, thiopyran,diketopyrrolopyrrole, polymethine, cinnamic acid esters and fluorescentdyes.

Particular preference is given to derivatives of arylamine andstyrylamine, for example TNB(=4,4′-bis[N-(1-naphthyl)-N-(2-naphthyl)amino]biphenyl). Metal-oxinoidcomplexes, such as LiQ or AlQ₃, can be used as co-hosts.

Preferred compounds with oligoarylene as matrix are disclosed in US2003/0027016 A1, U.S. Pat. No. 7,326,371 B2, US 2006/043858 A, WO2007/114358, WO 2008/145239, JP 3148176 B2, EP 1009044, US 2004/018383,WO 2005/061656 A1, EP 0681019B1, WO 2004/013073A1, U.S. Pat. No.5,077,142, WO 2007/065678 and DE 102009005746, where particularlypreferred compounds are described by the formulae H-2 to H-8.

Furthermore, compounds which can be employed as host or matrix includematerials which are employed together with phosphorescent emitters.

These compounds, which can also be employed as structural elements inpolymers, include CBP (N,N-biscarbazolylbiphenyl), carbazole derivatives(for example in accordance with WO 2005/039246, US 2005/0069729, JP2004/288381, EP 1205527 or WO 2008/086851), azacarbazoles (for examplein accordance with EP 1617710, EP 1617711, EP 1731584 or JP2005/347160), ketones (for example in accordance with WO 2004/093207 orin accordance with DE 102008033943), phosphine oxides, sulfoxides andsulfones (for example in accordance with WO 2005/003253),oligophenylenes, aromatic amines (for example in accordance with US2005/0069729), bipolar matrix materials (for example in accordance withWO 2007/137725), silanes (for example in accordance with WO2005/111172), 9,9-diarylfluorene derivatives (for example in accordancewith DE 102008017591), azaboroles or boronic esters (for example inaccordance with WO 2006/117052), triazine derivatives (for example inaccordance with DE 102008036982), indolocarbazole derivatives (forexample in accordance with WO 2007/063754 or WO 2008/056746),indenocarbazole derivatives (for example in accordance with DE102009023155 and DE 102009031021), diazaphosphole derivatives (forexample in accordance with DE 102009022858), triazole derivatives,oxazoles and oxazole derivatives, imidazole derivatives, polyarylalkanederivatives, pyrazoline derivatives, pyrazolone derivatives,distyrylpyrazine derivatives, thiopyran dioxide derivatives,phenylenediamine derivatives, tertiary aromatic amines, styrylamines,amino-substituted chalcone derivatives, indoles, hydrazone derivatives,stilbene derivatives, silazane derivatives, aromatic dimethylidenecompounds, carbodiimide derivatives, metal complexes of8-hydroxyquinoline derivatives, such as, for example, AlQ₃, which mayalso contain triarylaminophenol ligands (US 2007/0134514 A1), metalcomplex/polysilane compounds, and thiophene, benzothiophene anddibenzothiophene derivatives.

Examples of preferred carbazole derivatives are mCP(=1,3-N,N-dicarbazolylbenzene (=9,9′-(1,3-phenylene)bis-9H-carbazole))(formula H-9), CDBP(=9,9′-(2,2′-dimethyl[1,1′-biphenyl]-4,4′-diyl)bis-9H-carbazole),1,3-bis(N,N′-dicarbazolyl)benzene (=1,3-bis(carbazol-9-yl)benzene), PVK(polyvinylcarbazole), 3,5-di(9H-carbazol-9-yl)biphenyl and CMTTP(formula H-10). Particularly referred compounds are disclosed in US2007/0128467 A1 and US 2005/0249976 A1 (formulae H-11 and H-13).

Preferred tetraaryl-Si compounds are disclosed, for example, in US2004/0209115, US 2004/0209116, US 2007/0087219 A1 and in H. Gilman, E.A. Zuech, Chemistry & Industry (London, United Kingdom), 1960, 120.

Particularly preferred tetraaryl-Si compounds are described by theformulae H-14 to H-21.

Particularly preferred compounds from group 4 for the preparation of thematrix for phosphorescent dopants are disclosed, inter alia, in DE102009022858, DE 102009023155, EP 652273 B1, WO 2007/063754 and WO2008/056746, where particularly preferred compounds are described by theformulae H-22 to H-25.

With respect to the functional compounds which can be employed inaccordance with the invention and which can serve as host material,especial preference is given to substances which contain at least onenitrogen atom. These preferably include aromatic amines, triazinederivatives and carbazole derivatives. Thus, carbazole derivatives inparticular exhibit surprisingly high efficiency. Triazine derivativesresult in unexpectedly long lifetimes of the electronic devices.

It may also be preferred to employ a plurality of different matrixmaterials as a mixture, in particular at least one electron-conductingmatrix material and at least one hole-conducting matrix material.Preference is likewise given to the use of a mixture of acharge-transporting matrix material and an electrically inert matrixmaterial which is not in involved in the charge transport to asignificant extent, if at all, as described, for example, in WO2010/108579.

It is furthermore possible to employ compounds which improve thetransition from the singlet state to the triplet state and which,employed in support of the functional compounds having emitterproperties, improve the phosphorescence properties of these compounds.Suitable for this purpose are, in particular, carbazole and bridgedcarbazole dimer units, as described, for example, in WO 2004/070772 A2and WO 2004/113468 A1. Also suitable for this purpose are ketones,phosphine oxides, sulfoxides, sulfones, silane derivatives and similarcompounds, as described, for example, in WO 2005/040302 A1.

n-Dopants herein are taken to mean reducing agents, i.e. electrondonors. Preferred examples of n-dopants are W(hpp)₄ and otherelectron-rich metal complexes in accordance with WO 2005/086251 A2, P═Ncompounds (for example WO 2012/175535 A1, WO 2012/175219 A1),naphthylenecarbodiimides (for example WO 2012/168358 A1), fluorenes (forexample WO 2012/031735 A1), free radicals and diradicals (for example EP1837926 A1, WO 2007/107306 A1), pyridines (for example EP 2452946 A1, EP2463927 A1), N-heterocyclic compounds (for example WO 2009/000237 A1)and acridines as well as phenazines (for example US 2007/145355 A1).

Furthermore, the formulations may comprise a wide-band-gap material asfunctional material. Wide-band-gap material is taken to mean a materialin the sense of the disclosure content of U.S. Pat. No. 7,294,849. Thesesystems exhibit particularly advantageous performance data inelectroluminescent devices.

The compound employed as wide-band-gap material can preferably have aband gap of 2.5 eV or more, preferably 3.0 eV or more, particularlypreferably 3.5 eV or more. The band gap can be calculated, inter alia,by means of the energy levels of the highest occupied molecular orbital(HOMO) and the lowest unoccupied molecular orbital (LUMO).

Furthermore, the formulations may comprise a hole-blocking material(HBM) as functional material. A hole-blocking material denotes amaterial which prevents or minimises the transmission of holes (positivecharges) in a multilayer system, in particular if this material isarranged in the form of a layer adjacent to an emission layer or ahole-conducting layer. In general, a hole-blocking material has a lowerHOMO level than the hole-transport material in the adjacent layer.Hole-blocking layers are frequently arranged between the light-emittinglayer and the electron-transport layer in OLEDs.

It is basically possible to employ any known hole-blocking material. Inaddition to other hole-blocking materials described elsewhere in thepresent application, advantageous hole-blocking materials are metalcomplexes (US 2003/0068528), such as, for example,bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminium(III) (BAlQ).Fac-tris(1-phenylpyrazolato-N,C2)iridium(III) (Ir(ppz)₃) is likewiseemployed for this purpose (US 2003/0175553 A1). Phenanthrolinederivatives, such as, for example, BCP, or phthalimides, such as, forexample, TMPP, can likewise be employed.

Furthermore, advantageous hole-blocking materials are described in WO00/70655 A2, WO 01/41512 and WO 01/93642 A1.

Furthermore, the formulations may comprise an electron-blocking material(EBM) as functional material. An electron-blocking material denotes amaterial which prevents or minimises the transmission of electrons in amultilayer system, in particular if this material is arranged in theform of a layer adjacent to an emission layer or an electron-conductinglayer. In general, an electron-blocking material has a higher LUMO levelthan the electron-transport material in the adjacent layer.

It is basically possible to employ any known electron-blocking material.In addition to other electron-blocking materials described elsewhere inthe present application, advantageous electron-blocking materials aretransition-metal complexes, such as, for example, Ir(ppz)₃ (US2003/0175553).

The electron-blocking material can preferably be selected from amines,triarylamines and derivatives thereof.

Furthermore, the functional compounds which can be employed as organicfunctional materials in the formulations preferably have, if they arelow-molecular-weight compounds, a molecular weight of ≤3,000 g/mol, morepreferably ≤2,000 g/mol and most preferably ≤1,000 g/mol.

Of particular interest are furthermore functional compounds which aredistinguished by a high glass-transition temperature. In thisconnection, particularly preferred functional compounds which can beemployed as organic functional material in the formulations are thosewhich have a glass-transition temperature of ≥70° C., preferably ≥100°C., more preferably ≥125° C. and most preferably ≥150° C., determined inaccordance with DIN 51005.

The formulations may also comprise polymers as organic functionalmaterials. The compounds described above as organic functionalmaterials, which frequently have a relatively low molecular weight, canalso be mixed with a polymer. It is likewise possible to incorporatethese compounds covalently into a polymer. This is possible, inparticular, with compounds which are substituted by reactive leavinggroups, such as bromine, iodine, chlorine, boronic acid or boronic acidester, or by reactive, polymerisable groups, such as olefins oroxetanes. These can be used as monomers for the production ofcorresponding oligomers, dendrimers or polymers. The oligomerisation orpolymerisation here preferably takes place via the halogen functionalityor the boronic acid functionality or via the polymerisable group. It isfurthermore possible to crosslink the polymers via groups of this type.The compounds and polymers according to the invention can be employed ascrosslinked or uncrosslinked layer.

Polymers which can be employed as organic functional materialsfrequently contain units or structural elements which have beendescribed in the context of the compounds described above, inter aliathose as disclosed and extensively listed in WO 02/077060 A1, in WO2005/014689 A2 and in WO 2011/076314 A1. These are incorporated into thepresent application by way of reference. The functional materials canoriginate, for example, from the following classes:

-   Group 1: structural elements which are able to generate    hole-injection and/or hole-transport properties;-   Group 2: structural elements which are able to generate    electron-injection and/or electron-transport properties;-   Group 3: structural elements which combine the properties described    in relation to groups 1 and 2;-   Group 4: structural elements which have light-emitting properties,    in particular phosphorescent groups;-   Group 5: structural elements which improve the transition from the    so-called singlet state to the triplet state;-   Group 6: structural elements which influence the morphology or also    the emission colour of the resultant polymers;-   Group 7: structural elements which are typically used as backbone.

The structural elements here may also have various functions, so that aclear assignment need not be advantageous. For example, a structuralelement of group 1 may likewise serve as backbone.

The polymer having hole-transport or hole-injection properties employedas organic functional material, containing structural elements fromgroup 1, may preferably contain units which correspond to thehole-transport or hole-injection materials described above.

Further preferred structural elements of group 1 are, for example,triarylamines, benzidines, tetraaryl-para-phenylenediamines, carbazoles,azulenes, thiophenes, pyrroles and furanes and derivatives thereof andfurther O-, S- or N-containing heterocycles having a high HOMO. Thesearylamines and heterocycles preferably have an HOMO of above −5.8 eV(against vacuum level), particularly preferably above −5.5 eV.

Preference is given, inter alia, to polymers having hole-transport orhole-injection properties, containing at least one of the followingrecurring units of the formula HTP-1:

in which the symbols have the following meaning:

-   Ar¹ is, in each case identically or differently for different    recurring units, a single bond or a monocyclic or polycyclic aryl    group, which may optionally be substituted;-   Ar² is, in each case identically or differently for different    recurring units, a monocyclic or polycyclic aryl group, which may    optionally be substituted;-   Ar³ is, in each case identically or differently for different    recurring units, a monocyclic or polycyclic aryl group, which may    optionally be substituted;-   m is 1,2 or 3.

Particular preference is given to recurring units of the formula HTP-1which are selected from the group consisting of units of the formulaeHTP-1A to HTP-1C:

in which the symbols have the following meaning:

-   R^(a) is on each occurrence, identically or differently, H, a    substituted or unsubstituted aromatic or heteroaromatic group, an    alkyl, cycloalkyl, alkoxy, aralkyl, aryloxy, arylthio,    alkoxycarbonyl, silyl or carboxyl group, a halogen atom, a cyano    group, a nitro group or a hydroxyl group;-   r is 0, 1, 2, 3 or 4, and-   s is 0, 1, 2, 3, 4 or 5.

Preference is given, inter alia, to polymers having hole-transport orhole-injection properties, containing at least one of the followingrecurring units of the formula HTP-2:

-(T¹)_(c)-(Ar⁷)_(d)-(T²)_(e)-(Ar⁸)_(f)—  HTP-2

in which the symbols have the following meaning:

T¹ and T² are selected independently from thiophene, selenophene,thieno[2,3-b]thiophene, thieno[3,2-b]thiophene, dithienothiophene,pyrrole and aniline, where these groups may be substituted by one ormore radicals R^(b);

R^(b) is selected independently on each occurrence from halogen, —CN,—NC, —NCO, —NCS, —OCN, —SCN, —C(═O)NR⁰R⁰⁰, —C(═O)X, —C(═O)R⁰, —NH₂,—NR⁰R⁰⁰, —SH, —SR⁰, —SO₃H, —SO₂R⁰, —OH, —NO₂, —CF₃, —SF₅, an optionallysubstituted silyl, carbyl or hydrocarbyl group having 1 to 40 carbonatoms, which may optionally be substituted and may optionally containone or more heteroatoms;

-   R⁰ and R⁰⁰ are each independently H or an optionally substituted    carbyl or hydrocarbyl group having 1 to 40 carbon atoms, which may    optionally be substituted and may optionally contain one or more    heteroatoms;

Ar⁷ and Ar⁸ represent, independently of one another, a monocyclic orpolycyclic aryl or heteroaryl group, which may optionally be substitutedand may optionally be bonded to the 2,3-position of one or both adjacentthiophene or selenophene groups;

c and e are, independently of one another, 0, 1, 2, 3 or 4, where1<c+e≤6;

d and f are, independently of one another, 0, 1, 2, 3 or 4.

Preferred examples of polymers having hole-transport or hole-injectionproperties are described, inter alia, in WO 2007/131582 A1 and WO2008/009343 A1.

The polymer having electron-injection and/or electron-transportproperties employed as organic functional material, containingstructural elements from group 2, may preferably contain units whichcorrespond to the electron-injection and/or electron-transport materialsdescribed above.

Further preferred structural elements of group 2 which haveelectron-injection and/or electron-transport properties are derived, forexample, from pyridines, pyrimidines, pyridazines, pyrazines,oxadiazoles, quinolines, quinoxalines and phenazines and derivativesthereof, but also triarylboranes or further O-, S- or N-containingheterocycles having a low LUMO level. These structural elements of group2 preferably have an LUMO of below −2.7 eV (against vacuum level),particularly preferably below −2.8 eV.

The organic functional material can preferably be a polymer whichcontains structural elements from group 3, where structural elementswhich improve the hole and electron mobility (i.e. structural elementsfrom groups 1 and 2) are connected directly to one another. Some ofthese structural elements can serve as emitters here, where the emissioncolours may be shifted, for example, into the green, red or yellow.Their use is therefore advantageous, for example, for the generation ofother emission colours or a broad-band emission by polymers whichoriginally emit in blue.

The polymer having light-emitting properties employed as organicfunctional material, containing structural elements from group 4, maypreferably contain units which correspond to the emitter materialsdescribed above. Preference is given here to polymers containingphosphorescent groups, in particular the emitting metal complexesdescribed above which contain corresponding units containing elementsfrom groups 8 to 10 (Ru, Os, Rh, Ir, Pd, Pt).

The polymer employed as organic functional material containing units ofgroup 5 which improve the transition from the so-called singlet state tothe triplet state can preferably be employed in support ofphosphorescent compounds, preferably the polymers containing structuralelements of group 4 described above. A polymeric triplet matrix can beused here.

Suitable for this purpose are, in particular, carbazole and connectedcarbazole dimer units, as described, for example, in DE 10304819 A1 andDE 10328627 A1. Also suitable for this purpose are ketone, phosphineoxide, sulfoxide, sulfone and silane derivatives and similar compounds,as described, for example, in DE 10349033 A1. Furthermore, preferredstructural units can be derived from compounds which have been describedabove in connection with the matrix materials employed together withphosphorescent compounds.

The further organic functional material is preferably a polymercontaining units of group 6 which influence the morphology and/or theemission colour of the polymers. Besides the polymers mentioned above,these are those which have at least one further aromatic or anotherconjugated structure which do not count amongst the above-mentionedgroups. These groups accordingly have only little or no effect on thecharge-carrier mobilities, the non-organometallic complexes or thesinglet-triplet transition.

Structural units of this type are able to influence the morphologyand/or the emission colour of the resultant polymers. Depending on thestructural unit, these polymers can therefore also be used as emitters.

In the case of fluorescent OLEDs, preference is therefore given toaromatic structural elements having 6 to 40 C atoms or also tolan,stilbene or bisstyrylarylene derivative units, each of which may besubstituted by one or more radicals. Particular preference is given hereto the use of groups derived from 1,4-phenylene, 1,4-naphthylene, 1,4-or 9,10-anthrylene, 1,6-, 2,7- or 4,9-pyrenylene, 3,9- or3,10-perylenylene, 4,4′-biphenylene, 4,4″-terphenylylene,4,4′-bi-1,1′-naphthylylene, 4,4′-tolanylene, 4,4′-stilbenylene or4,4″-bisstyrylarylene derivatives.

The polymer employed as organic functional material preferably containsunits of group 7, which preferably contain aromatic structures having 6to 40 C atoms which are frequently used as backbone.

These include, inter alia, 4,5-dihydropyrene derivatives,4,5,9,10-tetrahydropyrene derivatives, fluorene derivatives, which aredisclosed, for example, in U.S. Pat. No. 5,962,631, WO 2006/052457 A2and WO 2006/118345 A1, 9,9-spirobifluorene derivatives, which aredisclosed, for example, in WO 2003/020790 A1, 9,10-phenanthrenederivatives, which are disclosed, for example, in WO 2005/104264 A1,9,10-dihydrophenanthrene derivatives, which are disclosed, for example,in WO 2005/014689 A2, 5,7-dihydrodibenzoxepine derivatives and cis- andtrans-indenofluorene derivatives, which are disclosed, for example, inWO 2004/041901 A1 and WO 2004/113412 A2, and binaphthylene derivatives,which are disclosed, for example, in WO 2006/063852 A1, and furtherunits which are disclosed, for example, in WO 2005/056633 A1, EP 1344788A1, WO 2007/043495 A1, WO 2005/033174 A1, WO 2003/099901 A1 and DE102006003710.

Particular preference is given to structural units of group 7 which areselected from fluorene derivatives, which are disclosed, for example, inU.S. Pat. No. 5,962,631, WO 2006/052457 A2 and WO 2006/118345 A1,spirobifluorene derivatives, which are disclosed, for example, in WO2003/020790 A1, benzofluorene, dibenzofluorene, benzothiophene anddibenzofluorene groups and derivatives thereof, which are disclosed, forexample, in WO 2005/056633 A1, EP 1344788 A1 and WO 2007/043495 A1.

Especially preferred structural elements of group 7 are represented bythe general formula PB-1:

in which the symbols and indices have the following meanings:

A, B and B′ are each, also for different recurring units, identically ordifferently, a divalent group, which is preferably selected from—CR^(c)R^(d)—, —NR^(c)—, —PR^(c)—, —O—, —S—, —SO—, —SO₂—, —CO—, —CS—,—CSe—, —P(═O)R^(c)—, —P(═S)R^(c)— and —SiR^(c)R^(d)—;

R^(c) and R^(d) are selected on each occurrence, independently, from H,halogen, —CN, —NC, —NCO, —NCS, —OCN, —SCN, —C(═O)NR⁰R⁰⁰, —C(═O)X,—C(═O)R⁰, —NH₂, —NR⁰R⁰⁰, —SH, —SR⁰, —SO₃H, —SO₂R⁰, —OH, —NO₂, —CF₃,—SF₅, an optionally substituted silyl, carbyl or hydrocarbyl grouphaving 1 to 40 carbon atoms, which may optionally be substituted and mayoptionally contain one or more heteroatoms, where the groups R^(c) andR^(d) may optionally form a spiro group with a fluorene radical to whichthey are bonded;

X is halogen;

R⁰ and R⁰⁰ are each, independently, H or an optionally substitutedcarbyl or hydrocarbyl group having 1 to 40 carbon atoms, which mayoptionally be substituted and may optionally contain one or moreheteroatoms;

g is in each case, independently, 0 or 1 and h is in each case,independently, 0 or 1, where the sum of g and h in a sub-unit ispreferably 1;

m is an integer ≥1;

Ar¹ and Ar² represent, independently of one another, a monocyclic orpolycyclic aryl or heteroaryl group, which may optionally be substitutedand may optionally be bonded to the 7,8-position or the 8,9-position ofan indenofluorene group; and

a and b are, independently of one another, 0 or 1.

If the groups R^(c) and R^(d) form a spiro group with the fluorene groupto which these groups are bonded, this group preferably represents aspirobifluorene.

Particular preference is given to recurring units of the formula PB-1which are selected from the group consisting of units of the formulaePB-1A to PB-1E:

where R^(c) has the meaning described above for formula PB-1, r is 0, 1,2, 3 or 4, and R^(e) has the same meaning as the radical R^(c).

R^(e) is preferably —F, —Cl, —Br, —I, —CN, —NO₂, —NCO, —NCS, —OCN, —SCN,—C(═O)NR⁰R⁰⁰, —C(═O)X, —C(═O)R⁰, —NR⁰R⁰⁰, an optionally substitutedsilyl, aryl or heteroaryl group having 4 to 40, preferably 6 to 20, Catoms, or a straight-chain, branched or cyclic alkyl, alkoxy,alkylcarbonyl, alkoxycarbonyl, alkylcarbonyloxy or alkoxycarbonyloxygroup having 1 to 20, preferably 1 to 12, C atoms, where one or morehydrogen atoms may optionally be substituted by F or Cl, and the groupsR⁰, R⁰⁰ and X have the meaning described above for formula PB-1.

Particular preference is given to recurring units of the formula PB-1which are selected from the group consisting of units of the formulaePB-1F to PB-1I:

in which the symbols have the following meaning:

L is H, halogen or an optionally fluorinated, linear or branched alkylor alkoxy group having 1 to 12 C atoms and preferably stands for H, F,methyl, i-propyl, t-butyl, n-pentoxy or trifluoromethyl; and

L′ is an optionally fluorinated, linear or branched alkyl or alkoxygroup having 1 to 12 C atoms and preferably stands for n-octyl orn-octyloxy.

For carrying out the present invention, preference is given to polymerswhich contain more than one of the structural elements of groups 1 to 7described above. It may furthermore be provided that the polymerspreferably contain more than one of the structural elements from onegroup described above, i.e. comprise mixtures of structural elementsselected from one group.

Particular preference is given, in particular, to polymers which,besides at least one structural element which has light-emittingproperties (group 4), preferably at least one phosphorescent group,additionally contain at least one further structural element of groups 1to 3, 5 or 6 described above, where these are preferably selected fromgroups 1 to 3.

The proportion of the various classes of groups, if present in thepolymer, can be in broad ranges, where these are known to the personskilled in the art. Surprising advantages can be achieved if theproportion of one class present in a polymer, which is in each caseselected from the structural elements of groups 1 to 7 described above,is preferably in each case ≥5 mol %, particularly preferably in eachcase ≥10 mol %.

The preparation of white-emitting copolymers is described in detail,inter alia, in DE 10343606 A1.

In order to improve the solubility, the polymers may containcorresponding groups. It may preferably be provided that the polymerscontain substituents, so that on average at least 2 non-aromatic carbonatoms, particularly preferably at least 4 and especially preferably atleast 8 non-aromatic carbon atoms are present per recurring unit, wherethe average relates to the number average. Individual carbon atoms heremay be replaced, for example, by O or S. However, it is possible for acertain proportion, optionally all recurring units, to contain nosubstituents which contain non-aromatic carbon atoms. Short-chainsubstituents are preferred here, since long-chain substituents can haveadverse effects on layers which can be obtained using organic functionalmaterials. The substituents preferably contain at most 12 carbon atoms,preferably at most 8 carbon atoms and particularly preferably at most 6carbon atoms in a linear chain.

The polymer employed in accordance with the invention as organicfunctional material can be a random, alternating or regioregularcopolymer, a block copolymer or a combination of these copolymer forms.

In a further embodiment, the polymer employed as organic functionalmaterial can be a non-conjugated polymer having side chains, where thisembodiment is particularly important for phosphorescent OLEDs based onpolymers. In general, phosphorescent polymers can be obtained byfree-radical copolymerisation of vinyl compounds, where these vinylcompounds contain at least one unit having a phosphorescent emitterand/or at least one charge-transport unit, as is disclosed, inter alia,in U.S. Pat. No. 7,250,226 B2. Further phosphorescent polymers aredescribed, inter alia, in JP 2007/211243 A2, JP 2007/197574 A2, U.S.Pat. No. 7,250,226 B2 and JP 2007/059939 A.

In a further preferred embodiment, the non-conjugated polymers containbackbone units, which are connected to one another by spacer units.Examples of such triplet emitters which are based on non-conjugatedpolymers based on backbone units are disclosed, for example, in DE102009023154.

In a further preferred embodiment, the non-conjugated polymer can bedesigned as fluorescent emitter. Preferred fluorescent emitters whichare based on non-conjugated polymers having side chains containanthracene or benzanthracene groups or derivatives of these groups inthe side chain, where these polymers are disclosed, for example, in JP2005/108556, JP 2005/285661 and JP 2003/338375.

These polymers can frequently be employed as electron- or hole-transportmaterials, where these polymers are preferably designed asnon-conjugated polymers.

Furthermore, the functional compounds employed as organic functionalmaterials in the formulations preferably have, in the case of polymericcompounds, a molecular weight M_(w) of ≥10,000 g/mol, particularlypreferably ≥20,000 g/mol and especially preferably ≥50,000 g/mol.

The molecular weight M_(w) of the polymers here is preferably in therange from 10,000 to 2,000,000 g/mol, particularly preferably in therange from 20,000 to 1,000,000 g/mol and very particularly preferably inthe range from 50,000 to 300,000 g/mol. The molecular weight M_(w) isdetermined by means of GPC(=gel permeation chromatography) against aninternal polystyrene standard.

The publications cited above for description of the functional compoundsare incorporated into the present application by way of reference fordisclosure purposes.

The formulations according to the invention may comprise all organicfunctional materials which are necessary for the production of therespective functional layer of the electronic device. If, for example, ahole-transport, hole-injection, electron-transport or electron-injectionlayer is built up precisely from one functional compound, theformulation comprises precisely this compound as organic functionalmaterial. If an emission layer comprises, for example, an emitter incombination with a matrix or host material, the formulation comprises,as organic functional material, precisely the mixture of emitter andmatrix or host material, as described in greater detail elsewhere in thepresent application.

Besides the said components, the formulation according to the inventionmay comprise further additives and processing assistants. These include,inter alia, surface-active substances (surfactants), lubricants andgreases, additives which modify the viscosity, additives which increasethe conductivity, dispersants, hydrophobicising agents, adhesionpromoters, flow improvers, antifoams, deaerating agents, diluents, whichmay be reactive or unreactive, fillers, assistants, processingassistants, dyes, pigments, stabilisers, sensitisers, nanoparticles andinhibitors.

The present invention furthermore relates to a process for thepreparation of a formulation according to the present invention, whereinthe at least first organic solvent, which is an alkyl benzoate, and theat least one organic functional material, which can be employed for theproduction of functional layers of electronic devices, are mixed.

A formulation in accordance with the present invention can be employedfor the production of a layer or multilayered structure in which theorganic functional materials are present in layers, as are required forthe production of preferred electronic or opto-electronic components,such as OLEDs.

The formulation of the present invention can preferably be employed forthe formation of functional layers on a substrate or one of the layersapplied to the substrate. The substrates can either have bank structuresor not.

The present invention likewise relates to a process for the productionof an electronic device in which a formulation according to the presentinvention is applied to a substrate and dried.

The functional layers can be produced, for example, by flood coating,dip coating, spray coating, spin coating, screen printing, reliefprinting, gravure printing, rotary printing, roller coating,flexographic printing, offset printing or nozzle printing, preferablyink-jet printing on a substrate or one of the layers applied to thesubstrate.

After the application of a formulation according to the presentinvention to a substrate or a functional layer already applied, a dryingstep can be carried out in order to remove the solvent from thecontinuous phase described above. The drying can preferably be carriedout at relatively low temperature and over a relatively long period inorder to avoid bubble formation and to obtain a uniform coating. Thedrying can preferably be carried out at a temperature in the range from80 to 300° C., more preferably 150 to 250° C. and most preferably 160 to200° C. The drying here can preferably be carried out at a pressure inthe range from 10⁻⁶ mbar to 2 bar, more preferably in the range from10⁻² mbar to 1 bar and most preferably in the range from 10⁻¹ mbar to100 mbar. During the drying process, the temperature of the substratescan be vary from −15° C. to 250° C. The duration of the drying dependson the degree of drying to be achieved, where small amounts of water canoptionally be removed at relatively high temperature and in combinationwith sintering, which is preferably to be carried out.

It may furthermore be provided that the process is repeated a number oftimes, with formation of different or identical functional layers.Crosslinking of the functional layer formed can take place here in orderto prevent dissolution thereof, as is disclosed, for example, in EP 0637 899 A1.

The present invention also relates to an electronic device obtainable bya process for the production of an electronic device.

The present invention furthermore relates to an electronic device havingat least one functional layer comprising at least one organic functionalmaterial which is obtainable by the above-mentioned process for theproduction of an electronic device.

An electronic device is taken to mean a device which comprises anode,cathode and at least one functional layer in between, where thisfunctional layer comprises at least one organic or organometalliccompound.

The organic electronic device is preferably an organicelectroluminescent device (OLED), a polymeric electroluminescent device(PLED), an organic integrated circuit (O-IC), an organic field-effecttransistor (O-FET), an organic thin-film transistor (O-TFT), an organic,light-emitting transistor (O-LET), an organic solar cell (O-SC), anorganic photovoltaic (OPV) cell, an organic, optical detector, anorganic photoreceptor, an organic field-quench device (O-FQD), anorganic electrical sensor, a light-emitting electrochemical cell (LEC)or an organic laser diode (O-laser), more preferably an organicelectroluminescent device (OLED) or a polymeric electroluminescentdevice (PLED).

Active components are generally the organic or inorganic materials whichare introduced between the anode and the cathode, where these activecomponents effect, maintain and/or improve the properties of theelectronic device, for example its performance and/or its lifetime, forexample charge-injection, charge-transport or charge-blocking materials,but in particular emission materials and matrix materials. The organicfunctional material which can be employed for the production offunctional layers of electronic devices accordingly preferably comprisesan active component of the electronic device.

Organic electroluminescent devices are a preferred embodiment of thepresent invention. The organic electroluminescent device comprises acathode, an anode and at least one emitting layer.

It is furthermore preferred to employ a mixture of two or more tripletemitters together with a matrix. The triplet emitter having theshorter-wave emission spectrum serves as co-matrix here for the tripletemitter having the longer-wave emission spectrum.

The proportion of the matrix material in the emitting layer in this caseis preferably between 50 and 99.9% by vol., more preferably between 80and 99.5% by vol. and most preferably between 92 and 99.5% by vol. forfluorescent emitting layers and between 85 and 97% by vol. forphosphorescent emitting layers.

Correspondingly, the proportion of the dopant is preferably between 0.1and 50% by vol., more preferably between 0.5 and 20% by vol. and mostpreferably between 0.5 and 8% by vol. for fluorescent emitting layersand between 3 and 15% by vol. for phosphorescent emitting layers.

An emitting layer of an organic electroluminescent device may alsoencompass systems which comprise a plurality of matrix materials(mixed-matrix systems) and/or a plurality of dopants. In this case too,the dopants are generally the materials whose proportion in the systemis the smaller and the matrix materials are the materials whoseproportion in the system is the greater. In individual cases, however,the proportion of an individual matrix material in the system may besmaller than the proportion of an individual dopant.

The mixed-matrix systems preferably comprise two or three differentmatrix materials, more preferably two different matrix materials. One ofthe two materials here is preferably a material having hole-transportingproperties and the other material is a material havingelectron-transporting properties. However, the desiredelectron-transporting and hole-transporting properties of themixed-matrix components may also be combined principally or completelyin a single mixed-matrix component, where the further mixed-matrixcomponent(s) fulfil(s) other functions. The two different matrixmaterials may be present here in a ratio of 1:50 to 1:1, preferably 1:20to 1:1, more preferably 1:10 to 1:1 and most preferably 1:4 to 1:1.Mixed-matrix systems are preferably employed in phosphorescent organicelectroluminescent devices. Further details on mixed-matrix systems canbe found, for example, in WO 2010/108579.

Apart from these layers, an organic electroluminescent device may alsocomprise further layers, for example in each case one or morehole-injection layers, hole-transport layers, hole-blocking layers,electron-transport layers, electron-injection layers, exciton-blockinglayers, electron-blocking layers, charge-generation layers (IDMC 2003,Taiwan; Session 21 OLED (5), T. Matsumoto, T. Nakada, J. Endo, K. Mori,N. Kawamura, A. Yokoi, J. Kido, Multiphoton Organic EL Device HavingCharge Generation Layer) and/or organic or inorganic p/n junctions. Itis possible here for one or more hole-transport layers to be p-doped,for example with metal oxides, such as MoO₃ or WO₃, or with(per)fluorinated electron-deficient aromatic compounds, and/or for oneor more electron-transport layers to be n-doped. It is likewise possiblefor interlayers, which have, for example, an exciton-blocking functionand/or control the charge balance in the electroluminescent device, tobe introduced between two emitting layers. However, it should be pointedout that each of these layers does not necessarily have to be present.These layers may likewise be present on use of the formulationsaccording to the invention, as defined above.

In a further embodiment of the present invention, the device comprises aplurality of layers. The formulation according to the present inventioncan preferably be employed here for the production of a hole-transport,hole-injection, electron-transport, electron-injection and/or emissionlayer.

The present invention accordingly also relates to an electronic devicewhich comprises at least three layers, but in a preferred embodiment allsaid layers, from hole-injection, hole-transport, emission,electron-transport, electron-injection, charge-blocking and/orcharge-generation layer and in which at least one layer has beenobtained by means of a formulation to be employed in accordance with thepresent invention. The thickness of the layers, for example thehole-transport and/or hole-injection layer, can preferably be in therange from 1 to 500 nm, more preferably in the range from 2 to 200 nm.

The device may furthermore comprise layers built up from furtherlow-molecular-weight compounds or polymers which have not been appliedby the use of formulations according to the present invention. These canalso be produced by evaporation of low-molecular-weight compounds in ahigh vacuum.

It may additionally be preferred to use the compounds to be employed notas the pure substance, but instead as a mixture (blend) together withfurther polymeric, oligomeric, dendritic or low-molecular-weightsubstances of any desired type. These may, for example, improve theelectronic properties or themselves emit.

In a preferred embodiment of the present invention, the formulationsaccording to the invention comprise organic functional materials whichare employed as host materials or matrix materials in an emitting layer.The formulation here may comprise the emitters described above inaddition to the host materials or matrix materials. The organicelectroluminescent device here may comprise one or more emitting layers.If a plurality of emission layers are present, these preferably have aplurality of emission maxima between 380 nm and 750 nm, resultingoverall in white emission, i.e. various emitting compounds which areable to fluoresce or phosphoresce are used in the emitting layers. Veryparticular preference is given to three-layer systems, where the threelayers exhibit blue, green and orange or red emission (for the basicstructure see, for example, WO 2005/011013). White-emitting devices aresuitable, for example, as backlighting of LCD displays or for generallighting applications.

It is also possible for a plurality of OLEDs to be arranged one abovethe other, enabling a further increase in efficiency with respect to thelight yield to be achieved.

In order to improve the coupling-out of light, the final organic layeron the light-exit side in OLEDs can, for example, also be in the form ofa nanofoam, resulting in a reduction in the proportion of totalreflection.

Preference is furthermore given to an organic electroluminescent devicein which one or more layers are applied by means of a sublimationprocess, in which the materials are applied by vapour deposition invacuum sublimation units at a pressure below 10⁻⁵ mbar, preferably below10⁻⁶ mbar, more preferably below 10⁻⁷ mbar.

It may furthermore be provided that one or more layers of an electronicdevice according to the present invention are applied by means of theOVPD (organic vapour phase deposition) process or with the aid ofcarrier-gas sublimation, in which the materials are applied at apressure between 10⁻⁵ mbar and 1 bar.

It may furthermore be provided that one or more layers of an electronicdevice according to the present invention are produced from solution,such as, for example, by spin coating, or by means of any desiredprinting process, such as, for example, screen printing, flexographicprinting or offset printing, but particularly preferably LITI (lightinduced thermal imaging, thermal transfer printing) or ink-jet printing.

These layers may also be applied by a process in which no compound ofthe formula (I) or (II) is employed. An orthogonal solvent canpreferably be used here, which, although dissolving the functionalmaterial of a layer to be applied, does not dissolve the layer to whichthe functional material is applied.

The device usually comprises a cathode and an anode (electrodes). Theelectrodes (cathode, anode) are selected for the purposes of the presentinvention in such a way that their band energies correspond as closelyas possible to those of the adjacent, organic layers in order to ensurehighly efficient electron or hole injection.

The cathode preferably comprises metal complexes, metals having a lowwork function, metal alloys or multilayered structures comprisingvarious metals, such as, for example, alkaline-earth metals, alkalimetals, main-group metals or lanthanoids (for example Ca, Ba, Mg, Al,In, Mg, Yb, Sm, etc.). In the case of multilayered structures, furthermetals which have a relatively high work function, such as, for example,Ag and Ag nanowire (Ag NW) can also be used in addition to the saidmetals, in which case combinations of the metals, such as, for example,Ca/Ag or Ba/Ag, are generally used. It may also be preferred tointroduce a thin interlayer of a material having a high dielectricconstant between a metallic cathode and the organic semiconductor.Suitable for this purpose are, for example, alkali-metal oralkaline-earth metal fluorides, but also the corresponding oxides (forexample LiF, Li₂O, BaF₂, MgO, NaF, etc.). The layer thickness of thislayer is preferably between 0.1 and 10 nm, more preferably between 0.2and 8 nm, and most preferably between 0.5 and 5 nm.

The anode preferably comprises materials having a high work function.The anode preferably has a potential greater than 4.5 eV vs. vacuum.Suitable for this purpose are on the one hand metals having a high redoxpotential, such as, for example, Ag, Pt or Au. On the other hand,metal/metal oxide electrodes (for example Al/Ni/NiO_(x), Al/PtO_(x)) mayalso be preferred. For some applications, at least one of the electrodesmust be transparent in order to facilitate either irradiation of theorganic material (O-SCs) or the coupling-out of light (OLEDs/PLEDs,O-lasers). A preferred structure uses a transparent anode. Preferredanode materials here are conductive, mixed metal oxides. Particularpreference is given to indium tin oxide (ITO) or indium zinc oxide(IZO). Preference is furthermore given to conductive, doped organicmaterials, in particular conductive, doped polymers, such as, forexample, poly(ethylenedioxythiophene) (PEDOT) and polyaniline (PANI) orderivatives of these polymers. It is furthermore preferred for a p-dopedhole-transport material to be applied as hole-injection layer to theanode, where suitable p-dopants are metal oxides, for example MoO₃ orWO₃, or (per)fluorinated electron-deficient aromatic compounds. Furthersuitable p-dopants are HAT-CN (hexacyanohexaazatriphenylene) or thecompound NDP9 from Novaled. A layer of this type simplifies holeinjection in materials having a low HOMO, i.e. an HOMO with a largevalue.

In general, all materials as are used for the layers in accordance withthe prior art can be used in the further layers, and the person skilledin the art will be able to combine each of these materials with thematerials according to the invention in an electronic device withoutinventive step.

The device is correspondingly structured in a manner known per se,depending on the application, provided with contacts and finallyhermetically sealed, since the lifetime of such devices is drasticallyshortened in the presence of water and/or air.

The formulations according to the invention and the electronic devices,in particular organic electroluminescent devices, obtainable therefromare distinguished over the prior art by one or more of the followingsurprising advantages:

-   1. The electronic devices obtainable using the formulations    according to the invention exhibit very high stability and a very    long lifetime compared with electronic devices obtained using    conventional methods.-   2. The formulations according to the invention can be processed    using conventional methods, so that cost advantages can also be    achieved thereby.-   3. The organic functional materials employed in the formulations    according to the invention are not subject to any particular    restrictions, enabling the process of the present invention to be    employed comprehensively.-   4. The coatings obtainable using the formulations of the present    invention exhibit excellent quality, in particular with respect to    the uniformity of the coating.

These above-mentioned advantages are not accompanied by an impairment ofthe other electronic properties.

It should be pointed out that variations of the embodiments described inthe present invention fall within the scope of this invention. Eachfeature disclosed in the present invention can, unless this isexplicitly excluded, be replaced by alternative features which serve thesame, an equivalent or a similar purpose. Thus, each feature disclosedin the present invention is, unless stated otherwise, to be regarded asan example of a generic series or as an equivalent or similar feature.

All features of the present invention can be combined with one anotherin any way, unless certain features and/or steps are mutually exclusive.This applies, in particular, to preferred features of the presentinvention. Equally, features of non-essential combinations can be usedseparately (and not in combination).

It should furthermore be pointed out that many of the features, and inparticular those of the preferred embodiments of the present invention,are themselves inventive and are not to be regarded merely as part ofthe embodiments of the present invention. For these features,independent protection can be sought in addition or as an alternative toeach invention presently claimed.

The teaching on technical action disclosed with the present inventioncan be abstracted and combined with other examples.

The invention is explained in greater detail below with reference toworking examples, but without being restricted thereby.

The person skilled in the art will be able to use the descriptions toproduce further electronic devices according to the invention withoutthe need to employ inventive skill and thus can carry out the inventionthroughout the range claimed.

WORKING EXAMPLES

Working examples 1 to 3 presented below were made using the devicestructure shown in FIG. 1. The hole-injection layer (HIL) and holetransport layer (HTL) of all examples were prepared by an inkjetprinting process to achieve the desired thickness.

Three devices were made, using the device structure shown in FIG. 1. Thegreen emissive layers (G-EML) are made in the solvents described asExample 1, Example 2, and Example 3. The solvents for G-EML are methylbenzoate (Example 1), ethyl benzoate (Example 2), and butyl benzoate(Example 3). For the HTL, HTM-1 was dissolved in 3-phenoxytoluene. Table2 summarizes the concentration, viscosity and surface tension of theinks used in these examples as green emissive layer material.

TABLE 2 Concentration, viscosity and surface tension of the inks forG-EML. Surface Conc Viscosity Tension Layer Ink Code (weight %) (mPas)(mN/m) G-EML Example 1 1.296 2.0 37.2 G-EML Example 2 1.333 2.1 34.7G-EML Example 3 1.386 3.9 33.6

The viscosity of the formulations and solvents was measured using a 1°cone-plate rotational rheometer (type: Haake MARS III Rheometer fromThermo Scientific), where the temperature and sheer rate are exactlycontrolled. The viscosities given in Table 2 are the viscosities of eachformulation measured at a temperature of 25° C. (+/−0.2° C.) and a sheerrate of 500 s⁻¹. The measurements were carried out with the followingsetup: Haake MARS III Rheometer with bottom plate TMP60 and cone C60/1°Ti L.; N₂ supply with a back-pressure of ˜1.8 bar; sample volume of 1.3ml.

Each formulation is measured three times. The stated viscosity value isaveraged over said measurements. The data processing is performed withthe software “Haake RheoWin Job Manager” in accordance with DIN 1342-2.The equipment (Haake MARS III from Thermo Scientific) is regularlycalibrated by Thermo Scientific and received a certified standardfactory calibration before its first use.

The surface tension measurements were performed using the high precisiondrop shape analysis tool DSA100 from Krüss GmbH. The surface tension isdetermined by the software “DSA4” in accordance with DIN 55660-1. Allmeasurements were performed at room temperature being in the rangebetween 22° C. and 24° C. The standard operating procedure includes thedetermination of the surface tension of each formulation (sample volumeof 0.3 ml) using a fresh disposable drop dispensing system (syringe andneedle). Each drop is measured over the duration of one minute withsixty measurements which are later on averaged. For each formulationthree drops are measured. The final value is averaged over saidmeasurements. The tool is regularly cross-checked against variousliquids having known surface tension.

Description of Fabrication Process

Glass substrates covered with pre-structured ITO and bank material werecleaned using ultrasonication in isopropanol followed by de-ionizedwater, then dried using an air-gun and a subsequent annealing on ahot-plate at 230° C. for 2 hours.

A hole-injection layer (HIL) using PEDOT-PSS (Clevios A14083, Heraeus)was inkjet-printed onto the substrate and dried in vacuum. The HIL wasthen annealed at 185° C. for 30 minutes in air.

On top of the HIL, a hole-transport layer (HTL) was inkjet-printed,dried in vacuum and annealed at 210° C. for 30 minutes in nitrogenatmosphere. As material for the hole-transport layer polymer HTM-1 wasused. The structure of the polymer HTM-1 is the following:

The green emissive layer (G-EML) was also inkjet-printed, vacuum driedand annealed at 160° C. for 10 minutes in nitrogen atmosphere. The inkfor the green emissive layer contained in all working examples two hostmaterials (i.e. HM-1 and HM-2) as well as one triplett emitter (EM-1).The materials were used in the following ratio: HM-1:HM-2:EM-1=40:40:20.Only the solvent(s) differ from example to example, as can be seen fromTable 2 above. The structures of the materials are the following:

All inkjet printing processes were performed under yellow light andunder ambient conditions.

The devices were then transferred into a vacuum deposition chamber wherethe deposition of a common hole blocking layer (HBL), anelectron-transport layer (ETL), and a cathode (Al) was done usingthermal evaporation (see FIG. 1). The devices were then characterized inthe glovebox.

In the hole blocking layer (HBL) ETM-1 was used as a hole-blockingmaterial. The material has the following structure:

In the electron transport layer (ETL) a 50:50 mixture of ETM-1 and LiQwas used. LiQ is lithium 8-hydroxyquinolinate.

Finally, the Al electrode is vapor-deposited. The devices were thenencapsulated in a glove box and physical characterization was performedin ambient air. FIG. 1 shows the device structure.

The device is driven with constant voltage provided by a Keithley 230voltage source. The voltage over the device as well as the currentthrough the device are measured with two Keithley 199 DMM multimeters.The brightness of the device is detected with a SPL-025Y brightnesssensor, a combination of a photodiode with a photonic filter. The photocurrent is measured with a Keithley 617 electrometer. For the spectra,the brightness sensor is replaced by a glass fiber which is connected tothe spectrometer input. The device lifetime is measured under a givencurrent with an initial luminance. The luminance is then measured overtime by a calibrated photodiode.

Results and Discussion

Table 3 summarizes the data collected for each example. The devices inthe examples show good performance, meaning good values for voltage,efficiency and lifetime. These results indicate that the new solventsystem provides a good film formation in pixels. This solvent systemprovides an alternative choice for ink-jet printing technology to reachthe device requirement in terms of performance. It also provides anopportunity to fit various ink-jet printing machines using differentheads, since a wide variety of alkyl benzoate solvents can be used.

TABLE 3 Luminance efficiency, external quantum efficiency, operationvoltage and device lifetime External Luminance quantum Operationefficiency at efficiency at voltage at Lifetime at 1000 cd/m² 1000 cd/m²1000 cd/m² 1000 cd/m² (cd/A) (%) (V) (hrs) Ex. 1 48.9 13.3 6.8 14,000Ex. 2 51.2 14 6.6 15,000 Ex. 3 52 14.2 5.9 20,000

Working Example 4

In this example, the HTL was processed using HTM-1 as in workingexamples 1 to 3, but it was dissolved in butyl benzoate instead of3-phenoxytoluene. Table 4 summarizes the concentration, viscosity andsurface tension of the ink used in this example for the preparation of aHTL layer.

TABLE 4 Concentration, viscosity and surface tension of the ink for HTL.Surface Conc Viscosity Tension Layer Ink Code (weight %) (mPas) (mN/m)HTL 0.495 4.6 32.9

1.-22. (canceled)
 23. A formulation containing at least one organic functional material and at least a first organic solvent, wherein said first organic solvent is an alkyl benzoate and the content of the alkyl benzoate is in the range from 50 to 100 vol. %, based on the total amount of solvents in the formulation.
 24. The formulation according to claim 23, wherein the first organic solvent is an alkyl benzoate according to general formula (I)

wherein R¹ is identical or different at each occurrence, and are D, F, Cl, Br, I, NO₂, CN, a straight-chain alkyl having from 1 to 20 carbon atoms or a branched or cyclic alkyl group having from 3 to 20 carbon atoms, in which one or more non-adjacent CH₂ groups may be replaced by —O—, —S—, —NR³—, —CON³—, —CO—O—, —C═O—, —CH═CH— or —C≡C—, and in which one or more hydrogen atoms may be replaced by F, or an aryl or heteroaryl group which has from 4 to 14 carbon atoms and may be substituted by one or more nonaromatic R³ radicals, and a plurality of substituents R³, either on the same ring or on the two different rings, may together in turn form a mono- or polycyclic, aliphatic, aromatic or heteroaromatic ring system, which may be substituted by a plurality of substituents R³; R² is a straight-chain alkyl group having from 1 to 20 carbon atoms or a branched or cyclic alkyl group having from 3 to 20 carbon atoms, in which one or more non-adjacent CH₂ groups non-adjacent to the —CO—O— group in general formula (I) may be replaced by —O—, —S—, —NR³—, —CONR³—, —CO—O—, —C═O—, —CH═CH— or —C≡C—, and in which one or more hydrogen atoms may be replaced by F, or an aryl or heteroaryl group which has from 4 to 14 carbon atoms and may be substituted by one or more nonaromatic R³ radicals, and a plurality of substituents R³, either on the same ring or on the two different rings, may together in turn form a mono- or polycyclic, aliphatic, aromatic or heteroaromatic ring system, which may be substituted by a plurality of substituents R³; R³ are identical or different at each instance, and are a straight-chain alkyl or alkoxy group having from 1 to 20 carbon atoms or a branched or cyclic alkyl or alkoxy group having from 3 to 20 carbon atoms, in which one or more non-adjacent CH₂ groups may be replaced by —O—, —S—, —CO—O—, —C═O—, —CH═CH— or —C≡C—, and in which one or more hydrogen atoms may be replaced by F, or an aryl or heteroaryl group which has from 4 to 14 carbon atoms and may be substituted by one or more nonaromatic R³ radicals and n is 0 to
 3. 25. The formulation according to claim 24, wherein the first organic solvent is an alkyl benzoate according to general formula (I) wherein R¹ is a straight-chain alkyl group having from 1 to 20 carbon atoms or a branched or cyclic alkyl group having from 3 to 20 carbon atoms, in which one or more non-adjacent CH₂ groups may be replaced by —O—, —S—, —CO—O—, —C═O—, —CH═CH— or —C≡C—, and in which one or more hydrogen atoms may be replaced by F, or an aryl or heteroaryl group which has from 4 to 14 carbon atoms and may be substituted by one or more nonaromatic R⁵ radicals, R² is a straight-chain alkyl group having from 1 to 20 carbon atoms or a branched or cyclic alkyl group having from 3 to 20 carbon atoms, and n is 0 or
 1. 26. The formulation according to claim 24, wherein the first organic solvent is an alkyl benzoate according to formula (I) wherein R² is a straight-chain alkyl group having from 1 to 4 carbon atoms, preferably 4 carbon atoms, and n is
 0. 27. The formulation according to claim 23, wherein the first solvent has a surface tension of ≥20 mN/m.
 28. The formulation according to claim 23, wherein the content of the first solvent is in the range from 75 to 100 vol.-%, based on the total amount of solvents in the formulation.
 29. The formulation according to claim 23, wherein the first solvent has a boiling point in the range from 150 to 350° C.
 30. The formulation according to claim 23, wherein the formulation comprises at least one second solvent which is different from the first solvent.
 31. The formulation according to claim 30, wherein the second solvent has a boiling point in the range from 150 to 350° C.
 32. The formulation according to claim 23, wherein the at least one organic functional material has a solubility in the first as well as in the second solvent in the range from 1 to 250 g/l.
 33. The formulation according to claim 23, wherein the formulation has a surface tension in the range from 15 to 80 mN/m.
 34. The formulation according to claim 23, wherein the formulation has a viscosity in the range from 1 to 50 mPa·s.
 35. The formulation according to claim 23, wherein the content of the at least one organic functional material in the formulation is in the range from 0.001 to 20 weight-%, based on the total weight of the formulation.
 36. The formulation according to claim 23, wherein the at least one organic functional material is selected from the group consisting of organic conductors, organic semiconductors, organic fluorescent compounds, organic phosphorescent compounds, organic light-absorbent compounds, organic light-sensitive compounds, organic photosensitisation agents and other organic photoactive compounds such as organometallic complexes of transition metals, rare earths, lanthanides and actinides.
 37. The formulation according to claim 36, wherein the at least one organic functional material is selected from the group consisting of fluorescent emitters, phosphorescent emitters, host materials, matrix materials, exciton-blocking materials, electron-transport materials, electron-injection materials, hole-conductor materials, hole-injection materials, n-dopants, p-dopants, wide-band-gap materials, electron-blocking materials and hole-blocking materials.
 38. The formulation according to claim 36, wherein the at least one organic functional material is an organic semiconductor selected from the group consisting of hole-injecting, hole-transporting, emitting, electron-transporting and electron-injecting materials.
 39. The formulation according to claim 38, wherein the at least one organic semiconductor is selected from the group consisting of hole-injecting, hole-transporting and emitting materials.
 40. The formulation according to claim 39, wherein the hole-injecting and hole-transporting material is a polymeric compound or a blend of a polymeric compound and a non-polymeric compound.
 41. The formulation according to claim 38, wherein the at least one emitting material is a mixture of two or more different compounds having a low molecular weight.
 42. A process for the preparation of the formulation according to claim 23, which comprises mixing the at least one organic functional material and the at least first solvent.
 43. A process for the preparation of an electroluminescent device which comprises preparing at least one layer of the electroluminescent device in that the formulation according to claim 23 is deposited on a surface and subsequently dried.
 44. An electroluminescent device, wherein at least one layer is prepared in that the formulation according to claim 23 is deposited on a surface and subsequently dried. 